Laser Scanner Signal Processing with Synchronized Digital Gain Control
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Solution Overview
Problem
Conventional laser scanning bar code symbol reading systems face challenges in maintaining fast response time and signal linearity over long distances due to limitations in automatic gain control (AGC) techniques, which are hindered by continuous gain adjustments and requirements for broad dynamic range handling.
Innovation Solution
A laser scanning bar code symbol reading system employing a multi-channel parallel cascaded signal processing subsystem with synchronized digital gain control (SDGC) and a start of scan (SOS) detector, utilizing multiple signal processing channels with different amplification and filtering stages to produce digital first derivative and intensity data signals for synchronized gain control and decode processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional automatic gain control (AGC) is used to handle broad dynamic range signals, then the system can process signals from varying distances, but the response time is slow due to continuous gain adjustments
Solution Approach 1:
The patent implements periodic gain adjustment synchronized with the laser scanning cycles. Instead of continuous gain changes, the system updates gain values at discrete intervals corresponding to each scanning cycle, achieving fast response time while maintaining adaptability to varying signal strengths from different distances
Solution Approach 2:
The system dynamically switches between different gain values based on the detected signal strength and distance, using multiple pre-configured gain stages. This dynamic adaptation allows the system to quickly respond to changing conditions without the sluggishness of continuous analog AGC adjustment
2Adaptability or versatility
If conventional AGC with continuous gain adjustments is used, then the system can adapt to varying signal strengths, but signal linearity is compromised during scanning cycles
Solution Approach 1:
The patent applies periodic gain adjustment synchronized with scanning cycles, maintaining constant gain throughout each complete scan. This ensures signal linearity is preserved during the scanning process while still adapting to different signal strengths between cycles, resolving the contradiction between adaptability and linearity
Solution Approach 2:
The patent segments the gain control into discrete stages corresponding to different distance ranges. Each stage maintains a fixed gain value to ensure linearity, while the system switches between stages based on detected signal strength, achieving both adaptability and linearity
3Measurement precision
If multi-stage analog gain control is implemented for far field scanning, then signal quality improves, but the system complexity and device requirements increase
Solution Approach 1:
The patent replaces complex multi-stage analog gain control circuitry with a digital signal processing approach. A single analog-to-digital converter captures the full dynamic range, and digital processing algorithms then apply the appropriate gain and filtering, significantly reducing hardware complexity while maintaining or improving signal quality
Solution Approach 2:
The system changes the operating parameters of the analog-to-digital converter and digital processing algorithms based on the detected signal strength and distance. By adjusting digital filtering characteristics and gain values software-based, the system achieves multi-stage processing效果 without the hardware complexity of actual multi-stage analog circuits
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves improved signal-to-noise ratio and dynamic range handling, enabling fast response time and signal linearity during scanning cycles, effectively addressing the limitations of prior AGC methods by implementing discrete gain changes synchronized with scanning cycles.
Implementation Method 1
collecting and processing light from the return laser beam to extract information modulated onto the scanned beam
Data Source
AI summary
A laser scanning symbol reading system includes an analog scan data signal processor for producing digital data signals, wherein during each scanning cycle, a light collection and photo-detection module generates an analog scan data signal corresponding to a laser scanned symbol, a multi-channel parallel scan data signal processor/digitizer processes the analog scan data signal along multiple cascaded multi-stage signal processing channels, to generate digital data signals corresponding thereto, while a synchronized digital gain control module automatically processes the digital data signals in response to start of scan (SOS) signals generated by a SOS detector. Each signal processing channel supports different stages of amplification and filtering using a different set of band-pass filtering and gain parameters in each channel, to produce multiple digital first derivative data signals, and/or multiple digital scan data intensity data signals, having different signal amplitudes and dynamic range characteristics for use in decode processing.